Dual Optimization in Phase Transfer Catalyzed Synthesis of Dibenzyl Sulfide using Response Surface Methodology

A new reaction protocol has been developed to prepare dibenzyl sulfide (DBS), a value-added organosulfur fine chemical, by utilizing toxic hydrogen sulfide (H2S). H2S absorbed in monoethanolamine (MEA) has been used as a sulfiding agent for benzyl chloride (BC) under liquid liquid phase-transfer-catalyzed condition. Response surface methodology was used to model and optimize the process parameters for simultaneous dual-maximization of BC conversion and DBS selectivity. BC/sulfide mole ratio, MEA/sulfide mole ratio, temperature, and catalyst concentration were chosen as independent variables, and conversion of BC and selectivity of DBS were chosen as responses. A quadratic regression model was derived with satisfactory prediction. Dual optimization with desirability function predicts a maximum BC conversion of 100% and a maximum DBS selectivity of 95.2% under experimental conditions: temperature 353 K, catalyst concentration 0.14 kmol/m(3), BC/sulfide mole ratio 2.83, MEA/sulfide mole ratio 3.7. The analysis of variance and regression with R-2 values of 0.9996 for BC conversion and 0.9833 for DBS selectivity confirm the good agreement of experimental results with predicted values and therefore, the models can be successfully used to predict the synthesis of DBS successfully.